A composition variable mirrored as --<slug> for a mounted sub-composition
(default or an explicit data-variable-values value) previously overrode any
same-named custom property the document already authored elsewhere (e.g. a
:root theme token), since the mirroring had no "already defined" guard —
unlike the two other emission paths, which already skip re-emitting when the
name collides with an authored definition. Extend that guard to the
sub-composition mount path in both the compiler (htmlBundler.ts) and the
runtime loader (compositionLoader.ts / getVariables.ts), so an authored
definition always wins; render-time --variables overrides still always win.
Miguel Ángel
406894061e